This invention relates to an improvement in magneto-resistive angular position sensors used, for example, to determine the angular position of a galvanometer rotor.
Typically these sensors include a permanent magnet mounted on the end of the rotating shaft and a planar sensor fixed in an opposed, close relationship to the pole face of the magnet. The magnet is mounted so that its pole face is off-center with respect to the axis of the rotor shaft, but the sensor is centered with respect to that axis so that as the rotor turns, the pole face of the magnet sweeps over different portions of the sensor plane. As the rotor turns, the sensor's varying electrical response is measured by an appropriate circuit which determines the instantaneous angular position of the rotor, for use, e.g., in feedback control of the galvanometer. Thermal expansion, bearing wear, and other factors can affect the accuracy of such sensors.